BUMI lots is something created by the BN government to burden the non-bumi buyers.
Lets say to cost to build 2 identical property is RM200,000. Developer wants to make 50% margin. So should sell RM400,000 per unit. Assume that 1 is bumi lot and the other is non-bumi lot. Bumi lots get 7% discount. So what does the developer do?
Selling price of 2 units = 2 x RM400,000 = RM800,000
Target margin = 50%.
Difference between non-bumi and bumi lot = 7%.
Assume non-bumi price = A
Then bumi price = (1-0.07)xA
Target total selling revenue = RM800,000 = A + (1-0.07)xA = A+0.93A = 1.93A
A = RM800,000/1.93 = RM414,508

So non-bumi lot sells for RM414,508
And bumi lot sells for RM414,508 - 7% = RM385,492.

So, the discount given to bumi, is added to the selling price of non-bumi units. The government wants to non-bumi to subsidise the bumi.